The use of water quality index and water pollution index in assessing the water quality and suitability of the river Molo water basin, Kenya Water quality analysis of the Molo water basin

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Nathan K. Kipsang
Joshua Kibet
John O. Adongo


Pollution; Sediment; Water pollution index; Water quality index


Water quality assessment has become a very essential scientific procedure for qualifying water for drinking and general purpose use, and better public health policy on clean water supply. Various tools have been employed to determine the status of water systems for drinking, industrial and general use. For the purpose of this study, water quality index (WQI) and the recently developed water pollution index (WPI) have been adopted to evaluate the water of the Molo water basin. The world health organization (WHO) has defined limits of these parameters beyond which the quality of water is considered unsuitable for a specific use. The study was carried out in December, 2021 during the dry season. In this contribution, pH, conductivity, TDS, salinity, major cations and anions, and selected heavy metals were explored. Of the major cations Na reported the highest concentration at 1800 mg/L whereas in the anion category, the Cl gave the highest concentration at 110 mg/L. The highest pH, TDS and salinity were 8.5, 146.33, and 282.67, respectively. The data obtained were used to determine the water quality index (WQI) and water pollution index (WPI) of the Molo water basin based on the world health organization (WHO) standards. The average WQI obtained was 57.47 indicating that the water is slightly polluted.  Also the average WPI obtained was 0.77 indicating that the water from the water basin is not of good quality. Sediment morphology and composition was also determined using energy dispersive X-ray spectroscopy (EDS). The findings showed the presence of heavy metal pollutants of concern which include lead, manganese and copper. Therefore, with respect to WQI, WPI and sediment morphology, the water basin is significantly polluted. There is need therefore for the government and health authorities to formulate policies aimed at regulating pollution activities which may endanger the Molo water basin.

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